KCNK9 and pulmonary arterial hypertension: Moreover, heterozygous loss-of-function variants in KCNK3 are associated with a different disorder, pulmonary arterial hypertension (PAH), an adult-onset, progressive and often fatal disease characterized by increased pulmonary arterial pressure in the absence of the common causes of pulmonary hypertension27; in addition, loss-of-function variants in the TASK-3 channel (KCNK9) are associated with a neurodevelopmental disorder, Birk-Barel syndrome28.